Cyclic siloxane plasticized polycarbonate composition

ABSTRACT

A plasticized polycarbonate composition comprising in admixture a high molecular weight aromatic carbonate polymer and a minor amount of a cyclic siloxane plasticizer.

This invention is directed to a plasticized polycarbonate compositioncomprising in admixture a high molecular weight aromatic carbonatepolymer and a minor amount of a particular cyclic siloxane plasticizer.

BACKGROUND OF THE INVENTION

Polycarbonate polymers are excellent molding materials as products madethereform have high impact strength, toughness, high transparency, widetemperature limits (high impact resistance below -60° C. and a ULthermal endurance rating of 115° C. with impact), good dimensionalstability, high creep resistance and electrical properties which qualifyit as sole support for current carrying parts.

Polycarbonates are, however, very difficult to fabricate from melts forthe reason that melts thereof have exceptionally high viscosities.Attempts to overcome this difficulty by the incorporation with thepolycarbonate of materials know to reduce the viscosity of other resinshave very generally been unsuccessful. Many standard viscosity controlagents appear to have little or no effect on the viscosity ofpolycarbonate. Other compounds known to lower the viscosity of resinscause degradation of polycarbonate resins. Some compounds,conventionally employed to improve the workability of polymers, producean embrittling effect on polycarbonates when they are mixed therewithand the resin is subjected to elevated temperatures as in molding. Stillother materials, while satisfactory stiffness modifying agents for otherplastics, are too volatile to be incorporated with polycarbonates sincepolycarbonates have much higher melting points than many otherthermoplastics.

From U.S. Pat. No. 3,751,519 it is known that certain phenyl substitutedcyclosiloxane and alkyl substituted phenyl substituted cyclosiloxaneswhen added to aromatic polycarbonates provide a composition which hasmold release properties.

DESCRIPTION OF THE INVENTION

It has been surprisingly discovered that, by admixing a minor amount ofa particular organic plasticizer with a high molecular weight aromaticcarbonate polymer, the resultant polycarbonate composition has reducedmelt viscosity and does not become brittle or degraded upon molding andthus retains its characteristic high impact strength.

In the practice of this invention, the cyclic siloxane plasticizeradditive is characterized by the following formula: ##STR1## wherein Ris independently selected from the group consisting of C₁ to C₃₆ alkyl,C₁ to C₃₆ alkoxy, aryloxy of 6 to 14 carbon atoms, aralkoxy of 7 to 36carbon atoms, halogen substituted aryl of 6 to 14 carbon atoms and C₅ toC₃₀ alkyl substituted aryl of 6 to 14 carbon atoms.

These cyclic siloxane plasticizers are prepared by methods known in theart. For example, these plasticizers are prepared by the hydrolysis ofthe halogen precursor or by isomerization or disproportionation of thelinear polymers. These methods are set forth in Walter Koll, Chemistryand Technology of Silicones, Academic Press, 1968, for example, which isincorporated herein by reference.

The amount of organic plasticizer employed in the practice of thisinvention may vary from 0.05 to about 5.0 parts per hundred parts ofaromatic carbonate polymer. Preferably, these organic plasticizers areemployed in amounts of from 0.25 to 2.0 parts per hundred parts ofaromatic carbonate polymer.

In the practice of this invention, the high molecular weight aromaticpolycarbonates that can be employed herein are homopolymers andcopolymers and mixtures thereof which have an I.V. of 0.40 to 1.0 dl./g.as measured in methylene chloride at 25° C. that are prepared byreacting a dihydric phenol with a carbonate precursor. Typical of someof the dihydric phenols that may be employed in the practice of thisinvention are bisphenol-A, (2,2-bis(4-hydroxyphenyl) propane),bis(4-hydroxphenyl) methane, 2,2-bis(4-hydroxy-3-methylphenyl) propane,4,4-bis(4-hydroxyphenyl) heptane,2,2-(3,5,3',5'-tetrachloro-4,4'-dihydroxydiphenyl) propane,2,2-(3,5,3',5'-tetrabromo-4,4'-dihydroxydiphenyl) propane,(3,3'-dichloro-4,4'-dihydroxydiphenyl) methane. Other dihydric phenolsof the bisphenol type are also available and are disclosed in U.S. Pat.Nos. 2,999,835, 3,028,365 and 3,334,154.

It is, of course, possible to employ two or more different dihydricphenols or a copolymer of a dihydric phenol with a glycol or withhydroxy or acid terminated polyester, or with a dibasic acid in theevent a carbonate copolymer or inter-polymer rather than a homopolymeris desired for use in the preparation of the aromatic carbonate polymersof this invention. Also employed in the practice of this invention maybe blends of any of the above materials to provide the aromaticcarbonate polymer.

The carbonate precursor may be either a carbonyl halide, a carbonateester or a haloformate. The carbonyl halides which can be employedherein are carbonyl bromide, carbonyl chloride and mixtures thereof.Typical of the carbonate esters which may be employed herein arediphenyl carbonate, di-(halophenyl) carbonates such as di-(chlorophenyl)carbonate, di-(bromophenyl) carbonate, di-(trichlorophenyl) carbonate,di-(tribromophenyl) carbonate, etc., di-(alklphenyl) carbonates such asdi(tolyl) carbonate, etc., di-(naphthyl) carbonate, di-(chloronaphthyl)carbonate, phenyl tolyl carbonate, chlorophenyl chloronaphthylcarbonate, etc., or mixtures thereof. The haloformates suitable for useherein include bis-haloformates of dihydric phenols (bischloroformatesof hydroquinone, etc.) or glycols (bishaloformates of ethylene glycol,neopentyl glycol, polyethylene glycol, etc.). While other carbonateprecursors will occur to those skilled in the art, carbonyl chloride,also known as phosgene, is preferred.

Also included are the polymeric derivatives of a dihydric phenol, adicarboxylic acid and carbonic acid. These are disclosed in U.S. Pat.No. 3,169,121 which is incorporated herein by reference.

The aromatic carbonate polymers of this invention may be prepared byemploying a molecular weight regulator, an acid acceptor and a catalyst.The molecular weight regulators which can be employed in carrying outthe process of this invention include monohydric phenols such as phenol,chroman-I, paratertiarybutylphenol, parabromophenol, primary andsecondary amines, etc. Preferably, phenol is employed as the molecularweight regulator.

A suitable acid acceptor may be either an organic or an inorganic acidacceptor. A suitable organic acid acceptor is a tertiary amine andincludes such materials as pyridine, triethylamine, dimethylaniline,tributylamine, etc. The inorganic acid acceptor may be one which can beeither a hydroxide, a carbonate, a bicarbonate, or a phosphate of analkali or alkaline earth metal.

The catalysts which are employed herein can be any of the suitablecatalysts that aid the polymerization of bisphenol-A with phosgene.Suitable catalysts include tertiary amines such as, for example,triethylamine, tripropylamine, N,N-dimethylaniline, quaternary ammoniumcompounds such as, for example, tetraethylammonium bromide, cetyltriethyl ammonium bromide, tetra-n-heptylammonium iodide, tetra-n-propylammonium bromide, tetramethylammonium chloride, tetramethyl ammoniumhydroxide, tetra-n-butyl ammonium iodide, benzyltrimethyl ammoniumchloride and quaternary phosphonium compounds such as, for example,n-butyltriphenyl phosphonium bromide and methyltriphenyl phosphoniumbromide.

Also, included herein are branched polycarbonates wherein apolyfunctional aromatic compound is reacted with the dihydric phenol andcarbonate precursor to provide a thermoplastic randomly branchedpolycarbonate.

These polyfunctional aromatic compounds contain at least threefunctional groups which are carboxyl, carboxylic anhydride, haloformylor mixtures thereof. Examples of these polyfunctional aromatic compoundswhich may be employed in the practice of this invention include:trimellitic anhydride, trimellitic acid, trimellityl trichloride,4-chloroformyl phthalic anhydride, pyromellitic acid, pyromelliticdianhydride, mellitic acid, mellitic anhydride, trimesic acid,benzophenonetetracarboxylic acid, benzophenonetetracarboxylic anhydrideand the like. The preferred polyfunctional aromatic compounds aretrimellitic anhydride or trimellitic acid or their haloformylderivatives.

Also, included herein are blends of a linear polycarbonate and abranched polycarbonate.

The composition of the instant invention is prepared by blending thehigh molecular weight aromatic polycarbonate with the additive byconventional methods.

Obviously, other materials can also be employed with the aromaticcarbonate polymer of this invention and include such materials asanti-static agents, pigments, thermal stabilizers, ultravioletstabilizers, reinforcing fillers and the like.

PREFERRED EMBODIMENT OF THE INVENTION

In order to more fully and clearly illustrate the present invention, thefollowing specific examples are presented. It is intended that theexamples be considered as illustrative rather than limiting theinvention disclosed and claimed herein. In the examples, all parts andpercentages are on a weight basis unless otherwise specified.

Example I

One hundred (100) parts of an aromatic polycarbonate, prepared from2,2-bis(4-hydroxyphenyl) propane and phosgene in the presence of an acidacceptor and a molecular weight regulator and having an intrinsicviscosity of about 0.57, is mixed with the additive listed in the Tableby tumbling the ingredients together in a laboratory tumbler. Theresulting mixture is then fed to an extruder which is operated at about265° C., and the extrudate is comminuted into pellets.

The pellets are than fed into a plastometer and the flow rate of thepolymer is measured according to ASTM D1238-70, Condition O. The meltflow rate is set forth in the Table.

Additionally, the pellets are injection molded at about 315° C. intotest specimens of about 5 by 1/2 by 1/2 inch thick. The impact strengthof these specimens is then measured according to the Izod test, ASTMD-256. The impact strength is set forth in the Table. The sample labeledCONTROL is the polycarbonate as prepared without additive.

                                      TABLE                                       __________________________________________________________________________                                        Melt Flow                                                           Amt. of Additive                                                                        Rate   Impact Strength                    Additive                  (Parts per Hundred)                                                                     (gr./10 min.)                                                                        (Ft./Lbs./In.)                     __________________________________________________________________________    CONTROL                   --        10.10  15.0                                ##STR2##                 0.6       14.62  15.8                                ##STR3##                 1.0       14.21  13.2                                ##STR4##                 0.2       13.68  16.2                                ##STR5##                 0.5       17.73  14.6                                ##STR6##                 0.3       18.75  14.4                               __________________________________________________________________________

It can be seen from the data in the Table that when the instant organicplaticizer is added to a high molecular weight aromatic polycarbonate,the resulting polycarbonate composition has reduced melt viscosity asshown by the higher melt flow rate while retaining impact strength.

It will thus be seen that the objects set forth above among those madeapparent from the preceding description are efficiently attained andsince certain changes may be made in carrying out the above process andin the composition set forth without departing from the scope of thisinvention, it is intended that all matters contained in the abovedescription shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:
 1. A plasticized polycarbonate compositioncomprising in admixture a high molecular weight aromatic carbonatepolymer and a minor amount of a cyclic siloxane plasticizer of thefollowing formula: ##STR7## wherein R is independently selected from thegroup consisting of C₁ to C₃₆ alkyl, aryloxy of 6 to 14 carbon atoms,aralkoxy of 7 to 36 carbon atoms, halogen substituted aryl of 6 to 14carbon atoms and C₅ to C₃₀ alkyl substituted aryl of 6 to 14 carbonatoms, wherein said alkyl substituted aryl is bonded to said siliconatom through an intervening oxygen atom.
 2. The composition of claim 1wherein the organic plasticizer is present in an amount of from 0.05 toabout 5.0 parts per hundred parts of aromatic carbonate polymer.
 3. Thecomposition of claim 1 wherein the aromatic carbonate polymer is derivedfrom bisphenol-A.
 4. The composition of claim 1 wherein the aromaticcarbonate polymer is a copolymer derived from bisphenol-A and tetrabromobisphenol-A.
 5. The composition of claim 1 wherein the organicplasticizer has the following formula: ##STR8##
 6. The composition ofclaim 1 wherein the organic plasticizer has the following formula:##STR9##